Saw chain

ABSTRACT

A saw chain for a power chain saw is provided and comprises drive links and side links that connect them, whereby alternatingly disposed on one and the other longitudinal side of drive links, in place of a side link, are a cutter link and a leading safety link. The cutter link has a cutter tooth and a leading depth limiter, whereby the safety link is provided with a projecting nose for support against the base of a cut. The nose extends in the direction toward the depth limiter. The safety link is provided with a side portion disposed in front of the nose. The side portion has an elevated contact surface, which, when the saw chain is curved in the reversing region, is disposed on the path of a top cutting edge of the cutter tooth, and when the saw chain is extended reaches at least nearly to the height of the depth limiter.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a chain for a power chain saw.

[0002] U.S. Pat. No. 4,562,762 discloses a saw chain for a power chainsaw and comprises drive links, side links that connect them, as well ascutter links and guard links. In this connection, the cutter links andguard links are respectively alternatingly disposed on the longitudinalsides of the drive links, whereby in the direction of travel, the guardlink is disposed ahead of the cutter link. The cutter link is providedon that surface thereof that faces the upper side of the chain with acurved contour that rises toward the cutter link with a nose that isformed on the end of the guard link and that when the saw chain isextended is disposed next to a depth limiter of the cutter link. In thisconnection, the outer end of the nose is disposed slightly below theupper point of the depth limiter, although the highest bulge of theguard link is disposed on the level of the depth limiter. In the curvedstate of the chain, the guard link is pivoted relative to the cutterlink in such a way that in the region of the nose the outer contour ofthe guard link is disposed upon the path of the top cutting edge of thecutter link. With the known saw chain, no re-sharpening is provided, andsuch could not even be carried out economically since it is not possibleto adapt the non-uniform curved contour of the guard link with simplemeans.

[0003] DE 37 43 226 A1 discloses a re-sharpened saw chain where guard orsafety links are provided that precede the cutter tooth. These safetylinks are supported on the base of the cut via a nose-shaped projection.For this purpose, the safety link is provided with a nose that extendscounter to the direction of travel toward the cutter tooth, with thenose overlapping the depth limiter of the cutter link. The nose isprovided with a portion that drops off counter to the direction oftravel, and that in the guide or reversing region is displaced onto themovement path.

[0004] It is therefore an object of the present invention to provide asaw chain with which it is possible to achieve a significantly improvedresult during the so-called plunging or cutting with the power chainsaw.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] This object, and other objects and advantages of the presentinvention, will appear more clearly from the following specification inconjunction with the accompanying schematic drawings, in which:

[0006]FIG. 1 shows the front end of a guide bar of a saw with a portionof one exemplary embodiment of an inventive saw chain;

[0007]FIG. 2 is an enlarged illustration of one unit, comprised of adrive link, side link, cutter link and safety link, in the new state ofthe cutter and safety links;

[0008]FIG. 3 is an enlarged illustration of an individual safety link;

[0009]FIG. 4 is an illustration in accordance with FIG. 1 showingre-sharpened cutter and safety links;

[0010]FIG. 5 is an illustration according to FIG. 2 in a state after afirst re-sharpening;

[0011]FIG. 6 shows a unit according to FIG. 2 in the re-sharpened statewith a sharpening tool;

[0012]FIG. 7 shows a unit according to FIG. 5 in the last sharpenedstate; and

[0013]FIG. 8 shows a variation of the embodiment of FIG. 3.

SUMMARY OF THE INVENTION

[0014] The saw chain of the present invention is comprised of drivelinks and side links that connect the drive links, whereby a cutter linkand a leading safety link are alternatingly disposed, in place of a sidelink, on one and the other longitudinal side of drive links, and thecutter link has a cutter tooth and a preceding depth limiter, wherebythe safety link is provided with a projecting nose for support on thebase of a cut, with the nose extending in the direction toward the depthlimiter, the safety link is furthermore provided with a side portionthat in the direction of travel of the saw chain is disposed ahead ofthe nose, and which has an elevated contact surface that, when the sawchain is curved in a reversing region, is disposed on the path of thetop cutting edge of the cutter tooth, and that when the saw chain isextended, reaches at least nearly to the height of the depth limiter.

[0015] Pursuant to the configuration of the present invention, the sideportion, in the new state of the saw chain, forms the contact surface ata higher level, and only in the sharpened state of the saw chain doesthe contact surface on the nose of the safety link lie upon the path ofthe re-sharpened top cutting edge. In this way, the operative oreffective contact surface can be kept constant in the various stages ofthe re-sharpening. In this connection, it is expedient to have a largecontact surface structurally available for each sharpening stage,whereby these surfaces can be placed in a radial position relative tothe path of the top cutting edge that is favorable with regard to acutting performance.

[0016] Pursuant to a preferred embodiment, when the saw chain is curved,the entire length of the contact surface is disposed at least nearlyupon the path of the top cutting edge. Furthermore, it is expedient,when the saw chain is extended, that the front end of the contactsurface, as viewed in the direction of travel, be disposed at the sameheight as the depth limiter. Also with this design a good cutting resultis achieved.

[0017] Pursuant to a further embodiment of the invention, there isprovided on the side portion, in front of the contact surface as viewedin the direction of travel, a guide surface for a re-sharpening tool. Inthis way, the re-sharpening of the depth limiter is simplified, and atthe same time an adaptation of the contact surface is achieved. In frontof the guide surface as viewed in the direction of travel, anindentation is preferably provided, so that the edge of the sharpeningtool is free, and hence an optimal support of the sharpening tool uponthe guide surface is ensured. As viewed in the longitudinal direction ofthe safety link, the indentation is preferably disposed nearly over thecenter point of a rear rivet-receiving opening.

[0018] Pursuant to a further embodiment of the invention, a transitionregion is provided between the contact surface and the nose. Theeffectiveness of this transition region is that during a later stage ofthe re-sharpening, another contact surface is formed on respective stepsat the transition region and moves upon the path of the top cuttingedge. Pursuant to another embodiment, a peak or crown can be formed.This crown operates in such a way that in the curved state of the sawchain, it is disposed somewhat beyond the path of the re-sharpened topcutting edge, and hence during the plunging or cutting with the powerchain saw, this crown serves as a contact surface relative to the baseof the groove.

[0019] At least one marking or indicator is expediently provided in theregion of the side portion and/or on the lower border thereof; thisindicator is, for example, embodied as a line that extends parallel tothe guide surface. This indicator serves for establishing a specifiedmagnitude of the re-sharpening, whereby with a plurality of indicatorsthe various sharpening states can be recognized. It is expedient toembody the indicator in the manner of an embossment or relief in thematerial of the safety link.

[0020] Further specific features of the invention will be described indetail subsequently.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0021] Referring now to the drawings in detail, FIG. 1 shows the frontportion of a guide bar 1, which includes a guide or reversing region 3in which is disclosed a guide star 2. Also illustrated is a portion of asaw chain 4, which is disposed upon the guide bar 1 and extends alongthe guide region 3. The saw chain 4 includes drive links 5 as well ascutter links 6, side or tie links 7 and safety links 9. Theaforementioned links are hingedly or pivotably interconnected by meansof rivets 8. Rivet receiving openings 18 can be seen on the respectivefirst and last drive link 5 of the saw chain portion illustrated in FIG.1.

[0022] Each of the cutter links 6 includes a cutter tooth 26 having atop cutting edge 11 and a leading depth gauge or limiter 12 as viewed inthe direction of travel R. Disposed ahead of each cutter link 6, in thedirection of travel R, is a safety link 9 that is provided on its outercontour with a tongue or side portion 13, and has a nose 14 directedtoward the depth limiter 12. The height of the top cutting edge 11determines a path 10, whereby the outer contour of the side portion 13is disposed on the path 10, as is clearly shown in FIG. 1.

[0023]FIG. 2 shows an enlarged illustration of one unit comprised of adrive link 5, a side link 7, a cutter link 6, and a safety link 9. Thearrow R indicates the direction of travel. The rivets 8 and rivetreceiving openings 18 coincide with those of FIG. 1. The cutter link 6includes a cutter tooth 26, on the upper edge of which is disposed thetop cutting edge 11. The depth limiter 12 is disposed ahead of the topcutting edge 11, in the direction of travel R, by a spacing determinedby a recess 27 in the cutter link 6. The height of the depth limiter 12is dimensioned such that its upper edge is disposed below the height ofthe top cutting edge 11 by a spacing A.

[0024] As further shown in FIG. 2, the safety link 9 includes theupwardly directed side portion 13 and the nose 14 that is directedtoward the cutter link 6, whereby in the stretched position of the sawchain pursuant to the illustration in FIG. 2, the nose 14 comes to restnext to the depth limiter 12. Provided at the lower border of the sideportion 13 is a marking or indicator 17. Disposed at the upper side ofthe side portion 13 is a contact surface 15, the front end of which, asviewed in the direction of travel R, is indicated by the referencenumeral 16. In the stretched position of the saw chain, this end 16 ofthe contact surface 15 forms the highest point, which is disposed atleast approximately at the same level as the highest point of the depthlimiter 12, so that the spacing B between these two high points ispractically zero. The embodiment of the cutter link 6 and of the safetylink 9 shown in FIG. 2 corresponds to the new state of the chain, as isalso illustrated in FIG. 1.

[0025]FIG. 3 shows an enlarged illustration of an individual safety link9. This safety link 9 has two rivet receiving openings 18 and 18′ thatare disposed one after the other at a specific spacing when viewed inthe direction of travel R. The rear region of the safety link 9, againas viewed in the direction of travel R, is provided with an upper tongueor side portion 13, the lower border of which is delimited by theindicator 17. The upper side of the side portion 13 is formed by thecontact surface 15 and a guide surface 21 that adjoins the end 16 of thecontact surface. Provided ahead of the guide surface 15 as viewed in thedirection of travel R is an indentation 19 that is disposedapproximately above a center point 23 of the rear rivet receivingopening 18′. At the upper edge, in the region ahead of the indentation19, the safety link 9 is embodied as a double hump 20.

[0026] Provided at the rear end of the safety link 9 is the nose 14, theupper side of which is delimited by a surface 28. Disposed between thecontact surface 15 of the side portion 13, and the surface 28 of thenose 14, is a transition region 22 that drops off more steeply than doesthe contact surface 15, and that extends to the surface 28 in a curve.The indicator 17 extends, as a straight line, parallel to the guidesurface 1.

[0027]FIG. 4 shows the front end of a guide bar 1 with a portion of asaw chain 4 that is guided thereover and essentially corresponds to theillustration of FIG. 1. Therefore, the same components have the samereference numerals as in the previously described figures. In contrastto FIG. 1, however, the cutter links 6 and safety links 9 in FIG. 4 arein a re-sharpened state, which is recognizable with the cutter link 6due to the large spacing between the top cutting edge 11 and the depthlimiter 12. With the safety link 9, the re-sharpened state can berecognized at the downwardly displaced guide surface 21, which due toappropriate ablation or removal is disposed closer to the indicator 17.If due to re-sharpening the guide surface 21 has approached theindicator 17 to such an extent, the side portion or tab 13 shown in FIG.3 has nearly entirely disappeared. At the rear edge of the guide surface21, there is then formed by the adjoining transition region 22 a peak orcrown 25 that in the guide or reversing region projects somewhat beyondthe path 10.

[0028]FIG. 5 shows the unit of FIG. 2 in a state after about one thirdof the usable tooth length has been re-sharpened. It is clear from thisillustration that the recess 27 in the cutter link 6 is considerablylarger, and hence also the top cutting edge 11 on the cutter tooth 26 isrecessed. In contrast to the new state, also the height of the depthlimiter 12 is reduced, and the beginning of the top cutting edge 11 inFIG. 5 is lower than in the new state of the saw chain. The spacing Abetween the respective heights of the top cutting edge 11 and of thedepth limiter 12 is therefore the same magnitude as in FIG. 2. As canfurthermore be seen from FIG. 5, the side portion 13 from FIG. 3 isnearly entirely missing, so that the guide surface 21′ is considerablymore closer to the indicator 17. As a consequence of this shifting ofthe guide surface 21′ to a lower level, there results between thehighest point on the crown 25 and the highest level of the depth limiter12 a recognizable spacing B. The remaining features coincide with thoseof FIG. 2, so that the reference numerals for the same components areidentical.

[0029]FIG. 6 shows the unit comprised of the drive link 5, the side link7, the cutter link 6, and the safety link 9 in a further sharpened statewith a sharpening tool in the form of a file 24 on the depth limiter 12and the guide surface 21″. FIG. 6 indicates the last sharpening statethat can be carried out, since in this case the top cutting edge 11 isalready displaced toward the rear by the maximum amount. As shown inFIG. 6, one edge of the file 24 is disposed in the region of the recess19, so that the file can rest well upon the guide surface 21″. The guidesurface 21″ and the upper edge of the depth limiter 12 are aligned withone another.

[0030] This alignment of the upper edge of the depth limiter 12 and theguide surface 21″ of the safety link 9 is also visible in FIG. 7, whichalso shows the unit in the state of the maximum re-sharpening. In thisconnection, the position of the guide surface 21″ coincides with thepreviously present indicator 17, which is still visible in FIG. 5. Inother words, it is also clear that upon reaching this indicator, nofurther re-sharpening is possible. FIG. 7 also shows that the spacing Abetween the height of the cutting edge 11 and the uppermost point of thedepth limiter 12 is still constant, and that the uppermost point of thedepth limiter 12 is disposed at the same level as the outer contour ofthe double hump 20.

[0031]FIG. 8 shows an enlarged illustration of an individual safety link9 that has a different configuration than does the embodiment of FIG. 3with respect to the transition region between the contact surface 15 andthe surface 28 of the nose 14. In the embodiment shown in FIG. 8, thereis provided between the contact surface 15 and the surface 28 adouble-stepped transition region 29 that includes two steps 30 and 31that respectively form contact surfaces at different levels. Thisarrangement has the advantage that as a consequence of there-sharpening, the steps 30 and 31, depending upon the stage,successively serve as contact surfaces and hence provide a larger curvedlength contact surface than was the case in the embodiment of FIG. 3. Inother respects, the reference numerals correspond for the samecomponents.

[0032] As can be seen from the preceding description of FIGS. 1 to 8,with the inventive saw chain 4 there results three re-sharpening phasesthat are disposed between the new state of FIG. 2 and the final state ofFIG. 7. The first phase includes the range of 0 to 18% usable toothlength in which the contact surface 15 is effective. The second phaseincludes the range of 19 to 36% of the usable tooth length in which thetransition region 22 or 29 is effective. Due to the smaller contactsurface of the embodiment in FIG. 5, the pointed crown 25 beyond theactual path 10 of the top cutting edge 11 compensates for the missingsurface. In the embodiment of FIG. 8, in place of the crown thereresults a larger contact surface in the respective steps 30, 31 than inthe previous embodiment. The third phase extends over the range of 37 to100% of the usable tooth length. In this case, the surface 28 at theupper side of the nose 14 is effective as the contact surface (see FIG.7).

[0033] Further embodiments relative to the shape of the side portion 13and of the nose 14 are also possible. For example, the length of thecontact surface 15 can be greater, as a result of which the indentation19 would be disposed somewhat more forwardly. An increase in the heightof the double hump 20 is also possible to a limited extent, whereby theforward hump could also project slightly beyond the rearward hump.

[0034] It has been shown that with a saw chain pursuant to the presentinvention the cutting results are good not only in the new state butalso in the re-sharpened state, and in particular during plunging orcutting with the power chain saw the result is improved and handling ofthe power chain saw is facilitated.

[0035] The specification incorporates by reference the disclosure ofGerman priority document 102 16 529.7 filed Apr. 15, 2002.

[0036] The present invention is, of course, in no way restricted to thespecific disclosure of the specification and drawings, but alsoencompasses any modifications within the scope of the appended claims.

1. A saw chain for a power chain saw, comprising: drive links; sidelinks for connecting said drive links; cutter links, each having acutter tooth with a top cutting edge, and, in the direction of travel ofsaid saw chain, a leading depth limiter; and safety links, wherein saidcutter links and said safety links are alternatingly disposed onopposite longitudinal sides of said drive links in place of some of saidside links, wherein each safety link is provided with a projecting nosethat extends in a direction toward a depth limiter of a following cutterlink, wherein each safety link is further provided with a side portionthat in said direction of travel of said saw chain is disposed ahead ofsaid nose, wherein said side portion has an elevated contact surfacethat, when said saw chain is curved in a reversing region, is disposedon a path of said top cutting edge of said cutter tooth, and whereinwhen said saw chain is extended, said contact surface reaches at leastnearly to a height of said depth limiter.
 2. A saw chain according toclaim 1, wherein when said saw chain is in a curved state, at leastnearly an entire length of said contact surface is disposed on said pathof said top cutting edge.
 3. A saw chain according to claim 1, whereinwhen said saw chain is extended, a front end of said contact surface, asviewed in said direction of travel, is disposed at the same level assaid depth limiter.
 4. A saw chain according to claim 1, wherein a guidesurface for a re-sharpening tool is provided on said side portion aheadof said contact surface as viewed in said direction of travel.
 5. A sawchain according to claim 4, wherein a contour of said contact surface isconformable via a re-sharpening of said depth limiter.
 6. A saw chainaccording to claim 4, wherein an indentation is provided ahead of saidguide surface when viewed in the direction of travel.
 7. A saw chainaccording to claim 6, wherein in a longitudinal direction of said safetylink, said indentation is disposed approximately over a center point ofa rear rivet receiving opening of said safety link.
 8. A saw chainaccording to claim 4, wherein a transition region is disposed betweensaid contact surface and said nose.
 9. A saw chain according to claim 8,wherein said transition region includes at least two steps that act ascontact surfaces in a re-sharpened state of said safety link.
 10. A sawchain according to claim 8, wherein an upper surface of said nose isdelimited by a surface that in a re-sharpened state of a safety linkacts as a contact surface and is disposed upon said path of said topcutting edge.
 11. A saw chain according to claim 1, wherein at least oneindicator is disposed in the region of said side portion.
 12. A sawchain according to claim 11, wherein said indicator is provided on alower border of said side portion.
 13. A saw chain according to claim11, wherein said indicator is embodied as a line that extends parallelto a guide surface that is provided on said side portion ahead of saidcontact surface when viewed in said direction of travel.
 14. A saw chainaccording to claim 11, wherein said indicator is embodied in arelief-like manner in material of said safety link.
 15. A saw chainaccording to claim 6, wherein ahead of said indentation, as viewed insaid direction of travel, an upper contour of said safety link isembodied as a double hump.